Research flood risk in estuaries and coastal areas were interested in many countries around the world. In Viet Nam,research problem about flood risk just started in recent years, in the past, flood management includes structural measures and non- structural are being focused. Currently, the flood mapping was reflecting through risk mapping. In the framework of the article, some results research about the risk assessment in risk mapping due to flooding in the Long Dai and Kien Gian riverine catchments, Quang Binh province is presented.

Vu Gia - Thu Bon (VGTB) river system with a catchment area of 10.350 km2, of which, 45.359 ha agricultural land, and a population of 1.7 million, has created an strongly developing economy with the main centre of Central region as Da Nang city. During recent years, beside flood, other impacts of drought, saline intrusion and/or human activities as hydro-power, deforestation, pollution from insdustrial production activities, etc, have caused great challenges for sustainable basin-water management. This paper is to provide some results of studying impacts of reservoir system operation on the downstream flow of Vu Gia – Thu Bon river basin, which should be a basis to propose the scientific-technological solutions to ensure the sustainable use of surface-water resourcesand protection ofVGTB river water resources.

In recent years, under the impact of extreme floods and climate change, some reservoirs made operational flood discharge caused flood at downstream areas, significantly influence to people's life and national economy, causing annoyance and confusion in public opinion. However, for many reasons, including the operational management and simulation tools to support reservoir owners should still confused and passive in emergency situations. So to solve this problem, the immediate need to develop simulatio tools based on existing technology to serve the operator during floods to ensure safety of the reservoir and downstream. This article presents and proposes a synchronization tool, capable of flood forecasting, executive managing reservoirs and downstream flooding for Tam Ky river basin in Quang Nam Province. This toolkit is the recommended first step and is capable of deploying to many other basin.

In flood discharge period while flow pass-through section of in-constructing rock fill weir the flow velocity may cause downstream slope slide and river bed scouring. Thus research of structure of slope protection in order to provide rock fill weir safety under high flood flow discharge will play important role. The paper presents the results of research of structure of concrete slab for protection of downstream slope of in-constructive rock fill weir.

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Nghiên cứu xây dựng bản đồ ngập lụt vùng hạ lưu sông Đắk Bla

Doan, Dang Dinh

Quan, Ngo Anh

Son, Nguyen Hoang

The, Nguyen Ngoc

In recent years, the big flood in central highlands of Viet Namusually occurs with high intensity. The operation of reservoir systems in upstream of Se San together with the complex of climate conditions lead to the flood management and reservoir operation become more difficult. The inundation maps in Se San basin are useful to help decision maker carry out the suitable plans for management and operation the reservoir system. The DHI software package is useful tool in water resources applications and flood inundation map. In this paper, the MIKE NAM and MIKE 11 model are applied to simulate runoff on Dak Bla river. The results show that the MIKE NAM and MIKE 11 model are suitable for flood routing on Dak Bla river with NASH in ranges 0.65 to 0.92. The historical flood in 2009 and the satellite image are used for verification inundated area which simulated. The inundation areas due to floods are mapped in downstream of Dak Bla river corresponding with Alarm water level 1, 2, 3+1m and 3+2 m at Kom Tum station.

Limited the use of saline water for irrigation is the salt concentration in the water will affect the growth and yield of crops, soil environment due to the accumulation of salt. Thus, studies using saline water for irrigation to its low impact on the growth, yield of crops and minimize the environmental impact on the land is a matter for concern.

For a scientific basis for using saline water for irrigation for agriculture, this paper introduces the initial research results on the effects of saline irrigation water when applied to drip irrigation methods for upland crops to sandy soil environment at Kim Son district, Ninh Binh province

There are many works have been constructed for stabilizing the vessel fairway to the port or storm shelters in the Central and South Central of Vietnam since 1993. Some of them were built effectively such as estuaries of Lo (Nghe An), Tung (Quang Tri), Khanh Hai, Dong Hai, Ca Na (Ninh Thuan)....

In general, when building these works, it is only based on meagre data, through a number of results calculated using a mathematical model while the experimental work on a physical model for the layout location, size has not been fully implemented. Therefore, many vessel fairways have occured sedimentation phenomenon after building training works at astuaries such as Tu Hien (Thua Thien - Hue, Sa Huynh and My A (Quang Ngai), Da Nong (Phu Yen), La Gi (Binh Thuan )... or causing coastal erosion in the area near the rivermouth such as La Gi and Ca Ty - Phan Thiet (Binh Thuan province).

The paper presents the phenomenon of coastal erosion after building training work at estuaries, using MIKE 21/3FM to research, suggest orientedly work for stabilization of river and coastal zone of Ca Ty - Phan Thiet estuary.

In flood discharge period while flow pass-through section of in-constructing rock fill weir, the flow velocity may cause downstream slope slide and river bed scouring. Thus research of structure of slope protection for safety of rock- filling weir under high flood flow discharge will play important role. The paper intends to present results of research of structure of steel gabion with rock filling for protection of downstream slope of the in-constructive rock fill weir.

In the context of urbanization and rapidly increasing population in rural areas, production activities develop and alternately distribute in residential areas, increasing rural domestic wastewater leads to environmental contamination. Decentralized wastewater treatment solution to each pollution source with low investment technology, simple operation and environmental friendliness is an appropriate choice and viable for rural areas. Wastewater treatment technology ABR is one of technology sorts towards this solution. This article presents some of achieved results in completing ABR technology for processing - reuse wastewater for paddy field irrigation